1. Field of the Invention.
The present invention relates generally to computer aided design (CAD) applications and geographic information systems (GIS), and in particular, to a method, apparatus, and article of manufacture for managing sequential operations involved in surface design and manipulation.
2. Description of the Related Art
Computer aided design (CAD) applications are traditionally used for creating and editing drawings (e.g., maps, floor plans, and engineering designs). Further, CAD applications enable users to create/modify highly precise and accurate drawings/maps. Civil engineers and surveyors, for whom precision and accuracy are of primary importance, have adopted CAD applications to speed data input and perform computations for design projects.
Geographic information systems (GIS) have been traditionally used for spatial analysis and mapping and allow users to store, retrieve, manipulate, analyze, and display geographically referenced data. In this regard, an arc/node data model is commonly used in the GIS industry to identify a polygon that is used in land analysis. The arc/node model enables efficient data storage and users to easily determine whether an object is inside or outside a polygon. However, traditional GIS have been aimed at general cartography and broad land-use analysis, and not precision design for the construction and management of real-world projects. In this regard, the geometric precision that many engineers require has not been provided by traditional GIS systems. Some GIS companies have attempted to use complex databases to model real-world objects. However, such databases are still built on points, lines, and polygons and cannot store geometric objects used in traditional CAD applications (e.g., true arcs or road spirals).
Many organizations have used both CAD and GIS tools in different departments to utilize the different specific features available. Further, data from original CAD drawings may be frequently imported or digitized for use in the GIS mapping environment. However, because of the limitations of GIS systems and/or CAD systems, during such a transition, data connectivity, accuracy, and geometric precision are often lost. Accordingly, what is needed is an integrated solution that provides the functionality and tools of a GIS system with the precision and accuracy of a CAD application.
In an attempt to address the above concerns, industry specific components were built on top of the CAD engine to address specialized needs and eventually, an integrated solution was developed (e.g., Autodesk Map™ or Autodesk Land Desktop™ software available from the assignee of the present invention). Integrated solutions attempt to provide GIS functionality (e.g., multiuser editing, polygon overlay and analysis, topology, thematic mapping, etc.) within a CAD application and spatial database. The integrated solution allows civil engineers the ability to integrate the precision engineering tasks (from CAD) (e.g., site, roadway, and hydrological design) with the spatial analysis tools and data management of GIS.
Some integrated solutions may provide solutions for a particular industry or field. For example, one such integrated solution may be tailored to land development professionals to provide a base level of functionality for land planners, surveyors, civil engineers, drafters, and anyone who creates supporting documents. Such an application may also provide a streamlined ability to communicate survey data to and from the field and/or provide transportation and site engineering tools, and hydrology and hydraulics design and analysis.
Drawings in an integrated solution are often associated with one or more projects and a single project can contain one or more drawings. In this regard, land development professionals may desire to generate a model of the earth's surface for a project. Such a surface model is a three-dimensional geometric representation of the surface of an area of land. Surface models may be made up of triangles that are created when points that make up the surface data are connected. The triangles may form a triangulated irregular network (TIN) surface. A TIN line is one of the lines that makes up the surface triangulation. To create TIN lines, the surface points that are closest together may be connected.
The surface data used to obtain the surface points (i.e., for the surface map) may comprise random point data (points taken at a variety of elevations and coordinates), a selected group of points, coordinate geometry (COGO) points (e.g., COGO point data stored in an external database 110), or points imported from a file. Alternatively, coordinates from blocks or lines at elevations in a drawing may be used.
In addition to points, surfaces may also be built from DEM files (Digital Elevation Models), contour, breakline, and boundary data. The vertices of a contour may be used as surface points, or the contours may be treated as breaklines that prevent triangulation lines from crossing the contours.
To build a surface accurately, more information than points and contours must be provided. For example, to prevent surface triangulation across features such as roads or stream, breaklines may be defined. Breaklines are constraint lines used by the model that represent abrupt changes in the surface. TIN lines may be drawn to and from breakline vertices, but they do not cross the breakline. By including boundaries in the surface definition, a user can control how the surface extends to its outer limits, and internal areas may be hidden to prevent triangulation from occurring.
In addition to the above, when editing/manipulating a surface, many operations may be conducted by a user. However, the prior art does not provide the ability to easily undo and/or change a previously conducted operation. Further, the user does not have the option to compare the effects that a single operation may have on a surface. Accordingly, what is needed, is a GIS/CAD system that enables a user to edit a surface while maintaining the ability to view and manipulate edit operations on an individual basis.